Why is the bsod blue when there are millions of colors to choose from?
So this one I don't have a source on, but the story that I heard was that it was originally a Black Screen of Death but was changed to blue. The reasoning given to me was that computer BIOS (not to be mistaken for modern EEPROM which serves the same function) can only display in black and white and so by changing the background to blue users were expected to recognize that the system had crashed but that the operating system was still running. Hence the error codes given were OS errors and not BIOS errors, making troubleshooting far easier.
But why blue? Since the BSoD is a crash handler, and so needs to be as simple as possible, using the simplest color depth possible is the best. Hence the use of 3-bit color which would run on any available monitor of the Windows 3.1 era. But why blue specificially? Well with that limitation in mind, the highest contrast (and easiest to read) difference between text and background that uses 3-bit color is white (111) text on a black (000) background. If that's out of the question as explained above, the second highest contrast is between white (111) text on a blue (001) background.
If when something new can run older software it's called backwards compatibility, why when something old can run newer software isn't called forwards compatibility?
It is, actually. However one rarely hears about such things anymore as devising a future-proof standard isn't exactly at the top of most developers' lists of things they want to accomplish. They're rather just sell you something new so they can get more money.